1. AGU 2016 - Jasper Bloemen - 16 December 2016
Lessons learned from xylem CO2 transport
research. Part I, CO2 efflux, internal CO2
transport and respiration
Jasper Bloemen, Mary Anne McGuire*, Doug P Aubrey, Kathy
Steppe and Robert O Teskey
*Presenting author
1

2. Crown
Stem/Branch
Roots/Soil
Respired CO2 diffuses into the atmosphere…
2

3. ...but a fraction of respired CO2 remains internal
CO2
<1 -26 %
AtmosphereTree
CO2CO2
CO2
CO2
CO2
CO2
CO2
CO2
Internal CO2 in trees
0.04%
CO2
CO2
3

4. Internal CO2 in trees: what do we know?
Implications for :
• Assessing woody tissue respiration
• A fraction of respired CO2 remains
internally
• Assessing woody tissue photosynthesis
• Internal CO2 as substrate for woody tissue
photosynthesis
• Assessing tree carbon allocation
• Role of xylem CO2 transport?
4

5. Internal CO2 transport impacts stem respiration
5
McGuire and Teskey (2004), Tree Physiology Teskey and McGuire (2007), Plant, Cell Environment
[CO2]S
Stem respiration:
RS= [CO2]S +JU + JX
JU
JX

6. Modelling CO2 efflux– How to account for internal CO2
6
After Hölttä and Kolari (2009), Tree Physiology

7. Assessing stem respiration
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8. Internal CO2Soil CO2 efflux
Respiration
Bloemen et al. (2015), Trees structure and function
Root respiration vs. root CO2 efflux
Soil CO2
efflux
Sap flow
8

9. Internal CO2 in trees - focus on roots
A fraction of respired CO2 is transported internally instead of diffusing into the soil
• We are underestimating the metabolic cost of root respiration
• Soil CO2 efflux is not equal to soil respiration
Bloemen et al. (2015), Trees structure and function
Species Fraction of root-
respired CO2
transported
internally (%)
Period
considered
Method Reference
Populus deltoides
Bartr.
50.0 Day and night Es and Ft flux analysis Aubrey et al.
(2009)
Eucalyptus PF1
clone
17.0 Daytime Isotope analysis Grossiord et al.
(2012)
24.0 11-15h (high
sap flow)
Isotope analysis Grossiord et al.
(2012)
Quercus robur L. 6 Day and night Tree girdling and Es
and Ft flux analysis
Bloemen et al.
(2014a)
18.9 12-16h (high
sap flow)
Tree girdling and Es
and Ft flux analysis
Bloemen et al.
(2014a)
9

10. Root-derived CO2 : xylem transport vs. soil CO2 efflux
10
Aubrey and Teskey (2009), New Phytologist

11. Use of girdling to quantify root respiration
11
Girdle
Ra: autotrophic component of respiration
Rh: heterotrophic component of respiration
Bloemen et al. (2014), New Phytologist

12. Underestimation of root respiration by “soil-centric”
measurements
12
Girdle
Ra: autotrophic component of respiration
Rh: heterotrophic component of respiration
Bloemen et al. (2014), New Phytologist

13. • Internal CO2 transport affects stem respiration
• Need to quantify both internal and external fluxes of respired
CO2
• Use of mass balance approach
• Root respiration contributes to internal CO2 in tree stems
• Root-respired CO2 is transported aboveground where it can
diffuse to the atmosphere
• Underestimation by „soil-centric“ measurements
• Internal CO2 transport has important implications for our
understanding of carbon dynamics
Conclusions
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14. Dr. Doug Aubrey
Prof. dr. Robert O. Teskey
Dr. Mary Anne McGuire
Dr. ir. Jasper Bloemen
Prof. dr. ir. Kathy Steppe
14
Jasper Bloemen
Institute of Ecology, University of Innsbruck
Jasper.Bloemen@Uibk.ac.at
Bloemen.jasper@gmail.com